How many new shares could a public company issue

The company will have the number of shares that it is legally permitted to issue in its articles of incorporation (in the US). If the number of outstanding shares (e.g. already listed on exchange) is less than the amount authorized, the company can issue up to the authorized amount.

The company requires approval from its board of directors to increase the number of authorized shares.

The number of authorized shares is disclosed in the companys' 10-Q.